This project will examine the diverse actions of angiopoietins on airway blood vessels and lymphatic vessels with the goal of understanding underlying mechanisms of airway inflammation and developing new treatment strategies. Our recent findings of potent angiopoietin actions in airways have opened new directions with potentially important clinical implications. The angiopoietin growth factor family is essential for normal vascular development and plays a unique role in airway pathophysiology through Tie2 tyrosine kinase receptor signaling in endothelial cells. Angiopoietin-1 (Ang1) activates Tie2 receptor phosphorylation, whereas Angiopoietin-2 (Ang2) inhibits Ang1 actions or activates Tie2 signaling, depending on context and local temporal and spatial concentrations. The proposed project builds on results of studies of angiopoietin actions in airways during the current grant period and also benefits from complementary studies of angiogenesis and lymphangiogenesis in chronic airway inflammation and tumors in other projects. The overall hypothesis is that Ang1 and Ang2 facilitate the transition from acute to sustained airway inflammation through actions on endothelial cells of blood vessels and lymphatics. The four Specific Aims are to: (1) determine whether Ang1 reduces plasma leakage in airway inflammation by stabilizing endothelial cell junctions or pericyte associations;(2) determine the effect of Ang1-induced vascular remodeling on the responsiveness of airway vasculature to inflammatory stimuli;(3) determine whether Ang1 stabilizes the airway vasculature by limiting sprouting angiogenesis and vascular regression, and if Ang2 has the opposite effects;and (4) determine whether angiopoietins promote remodeling of lymphatic endothelial cells and fluid and cellular transport via airway lymphatics. Planned studies will use a combination of animal models of airway angiogenesis and inflammation in normal, transgenic, and knockout mice and in vitro studies of cultured endothelial cells to explore the cellular and molecular mechanisms of angiopoietin actions on blood vessels and lymphatic vessels. The approaches will take advantage of novel angiopoietin agonists and antagonists delivered as recombinant proteins or adenoviral vectors, state-of-the-art confocal microscopic imaging and quantification, and physiological and molecular methods. By elucidating the diverse actions of Ang1 and opposing or complementary actions of Ang2 that reduce plasma leakage, limit sprouting angiogenesis, and promote remodeling of airway blood vessels and lymphatic vessels, the planned studies will expand the perspective for developing future generations of therapies for asthma, chronic bronchitis, and other inflammatory airway diseases.